Aromatic compositions for treating silver images

ABSTRACT

A COMPOSITION FOR TREATING A SILVER IMAGE, SUCH AS THAT OBTAINED BY THE PHOTOGRAPHIC SILVER SALT DIFFUSION TRANSFER PROCESS ON A HYDROPHILIC SURFACE, COMPRISES AN ACIDIC AQUEOUS SOLUTION CONTAINING: (A) A LONG CHAIN AROMATIC CATIONIC COMPOUND, SUCH AS A LONG CHAIN ORGANIC QUATERNARY AMMONIUM COMPOUND, OR A LONG CHAIN ORGANIC SULPHONIUM COMPOUND, 8B) IODIDE IONS, AND 8C) A HETEROCYCLIC ORGANIC COMPOUND WHICH HAS A NITRO GROUP BONDED TO AN AROMATIC NUCLEUS, SUCH AS 1-(2&#39;&#39;,4-DINETROPHENYL) PYRIDIUM CHLORIDE, OR AN ORGANIC CATIONIC COMPOUND HAVING AN AROMATIC GROUP BUT NOT NITRO GROUP. A PRINTING PLATE COMPRISING A HYDROPHILIC SURFACE HAVING A SILVER IMAGE THEREON WHICH HAS BEEN TREATED WITH THIS COMPOSITION, AND A PROCESS FOR PREPARING SAID PLATE COMPRISING CONTACTING A SILVER IMAGE ON A HYDROPHILIC SURFACE WITH THIS COMPOSITIONS, ARE TAUGHT.

United States Patent Oftice 3,832,175 Patented Aug. 27, 1974 US. Cl. 96-29 L 21 Claims ABSTRACT OF THE DISCLOSURE A composition for treating a silver image, such as that obtained by the photographic silver salt diffusion transfer process on a hydrophilic surface, comprises an acidic aqueous solution containing:

(a) a long chain organic aromatic cationic compound, such as a long chain organic quaternary ammonium compound, or a long chain organic sulphonium compound,

(b) iodide ions, and

(c) a heterocyclic organic compound Which has a nitro group bonded to an aromatic nucleus, such as 1-(2,4'-dinitrophenyl) pyridinium chloride, or an organic cationic compound having an aromatic group but no nitro group.

A printing plate comprising a hydrophilic surface having a silver image thereon which has been treated with this composition, and a process for preparing said plate comprising contacting a silver image on a hydrophilic surface with this composition, are taught.

BACKGROUND OF THE INVENTION The present invention relates to lithographic processes and to lithographic printing plates made photographically. More particularly, this invention relates to a method of rendering oleophilic a silver image which has been produced by the photographic silver salt diffusion transfer process at a water accepting surface, such as the surface of a hydrophilic colloid layer or the surface of a layer of a hydrophilic pigment in a binder, so that the silver image accepts greasy printing ink. This invention also relates to the composition for treating the image and to the treated printing plates.

In lithography, a greasy ink is employed and the printing plate usually comprises a layer which, when wet with water, is hydrophilic and carries a line or dot image which is oleophilic.

Accordingly, a lithographic printing plate blank comprises a layer, the nature of whose surface is such that when wetted with water it will not accept greasy ink, although, if the ink is applied when the surface is dry, the ink so applied is not removed by subsequent wetting.

The practice of making a photolithographic printing plate is to produce an image at the surface of the hydrophilic layer which is sufficiently strong oleophilic to accept ink in the presence of water.

Where only a few hundreds of copies are required, or even up to about a thousand copies, it is quite common to use a paper printing plate, but where many thousands of copies are required, it is necessary to use a more substantial printing plate, and the ones commonly used are made of aluminum sheet or zinc sheet. From these metal sheets, it is a common practice in the art to take as many as twenty thousand copies. Aluminum sheet employed in the art is provided with an inert hydrophilic surface. This is often done by treating the aluminum to produce thereon an aluminum compound which is hydrophilic, for instance, aluminum oxide, as in the case of anodized aluminum, aluminum silicate and chromatized aluminum.

Various methods of obtaining a silver image on a lithographic printing plate blank can be used in a preferred process involving the photographic silver salt diffusion transfer process, in which diffusing silver halide complex contacts silver precipitating nuclei on the surface of a lithographic plate to deposit a silver image. This silver image is then treated with a fix solution containing an oleophilic compound which is adsorbed to the silver image to improve its affinity for a greasy printing ink.

DESCRIPTION OF THE PRIOR ART Hepher et al., US Pat. 3,161,508, issued Dec. 15, 1964, discloses organic compounds which may be used to treat the silver image to make it oleophilic. Suitable compounds include those containing a thiol group, oleophilic organic compounds generating a thiol group, and selenium analog organic compounds.

De Haes et al., US. Pat. 3,186,842, issued June 1, 1965, indicates that the silver image can be treated with a lithographic preparation containing a quaternary ammonium compound; such as, cetyl trimethylammonium bromide or the like, and a compound containing a mercapto group; such as, Z-mercapto-benzthiazole or the like.

There has been a continuing search for treating compositions which would render the silver image more oleophilic with regard to greasy printing inks or to improve ink-up time in which the image accepts ink. Accordingly, it is one object of this invention to provide a composition for improving the oleophilic character of the silver image. An additional object of this invention is to provide a process for improving the afiinity of silver images for greasy ink.

SUMMARY OF THE INVENTION According to the present invention, there is provided a method of rendering oleophilic a silver image, particularly one which has been produced by the photographic silver salt diffusion transfer process, on a water-accepting surface. This method comprises contacting the silver image With an acidic aqueous fix solution containing:

(a) a long chain (alkyl having 1220 carbon atoms) aromatic organic cationic compound,

(b) iodide ions, and

(c) a heterocyclic organic compound with a nitro group bonded to an aromatic nucleus or an aromatic cationic compound with no nitro group.

In one embodiment of the invention, a composition is provided for treating the silver image, which composition contains:

(a) a long chain organic aromatic quaternary ammonium compound,

(b) iodide ions, and

(c) a heterocyclic organic compound with a nitro group bonded to an aromatic nucleus or an aromatic cationic compound with no nitro group.

In preferred embodiments, the acidic aqueous solution contains a water-miscible alcohol having one or more hydroxy groups; e.g., methanol, and/or isopropanol and/ or isobutanol so as to increase the solubility of the solutes to the desired level. The long chain organic cationic compound is preferably cetyl pyridinum chloride or bromide; the iodide ions are supplied by potassium iodide, and the organic compound having a nitro group bonded to an aromatic nucleus is 1-(2',4-dinitrophenyl) pyridinium chloride or 8-nitroquinoline.

A heterocyclic organic compound having a nitro group bonded to an aromatic nucleus is preferably employed as the component (c) when the silver image requires more oxidation as a step in the process of rendering the silver oleophilic. Whether or not more oxidation is required 3 depends in part on the structure of the silver. If the silver is very porous the compound having a nitro group is likely to oxidize the silver too much.

By the process of this invention, a printing plate is provided comprising a silver image on a hydrophilic surface, which has been treated with the above acidic aqueous fix solution in order to improve the affinity for greasy printing ink.

DESCRIPTION OF THE PREFERRED EMBODIMENTS By the process of this invention, a printing plate is provided comprising a silver image on a hydrophilic surface, which image has been treated with the above acidic aqueous fix solution in order to improve the affinity for greasy printing ink.

LONG CHAIN CATIONIC COMPOUND In the present invention there may be used as the long chain organic cationic compound any of the cationic surfactants described in chapters 2 and 3 of Cationic Surfactants, edited by E. Jungermann and published by Marcel Dekker Inc., New York, 1970.

Broad classes of long chain organic aromatic cationic compounds which may be used are represented by the following formulae:

wherein R represents a long alkyl chain of 12 to 20 carbon atoms, each of R and R" may be either a long alkyl chain or a smaller alkyl or aryl group of 1-20 carbon atoms, R" is aryl having 6 to 20 carbon atoms and X represents an anion. Y represents a moiety containing an anion such as ZCH CO'6, or ZCH CH OS in which Z is a halide ion. The compounds employed may contain additional groups in the long chain such as -CONH-- and may contain more than one cationic N atom.

Preferred long chain cationic compounds for use in this invention may be represented by formulas I and II.

wherein R, R, R and R' are each an alkyl or aralkyl group of 1-20 carbon atoms, at least one of R, R, R" and R being an alkyl group containing at least 12 carbon atoms and X is a halogen ion other than iodide or a sulphate ion, or

wherein R is an alkyl group as defined above or aralkyl having 6-20 carbon atoms and X is halogen or sulphate ion.

Some compound of formula II may also function as the aromatic cationic compound with no nitro group, in which case a compound from group (c) will not be required. Such a compound is l-cetyl pyridinum bromine.

Long chain aromatic cationic compounds which can be used include, preferably, those with 12 to 20 carbon atoms in the long chain; for example, cationic compounds having an aliphatic group such as lauryl, tridecyl, myristyl, cetyl, stearyl, arachidyl, etc. Quaternary salts of organic nitrogen bases are especially suitable, such as e.g.,

quaternary ammonium compounds, etc. Also appropriate are polyonium salts having a quaternary ammonium-, a phosphoniumor a ternary sulfonium group which is linked to the onium-atom by an organic bivalent radical also linked to another onium group. Compounds having a long chain aliphatic group such as cetyl trimethylammonium bromide are particularly useful. The preferred compounds are long chain organic quaternary ammonium compounds or long chain sulfonium compounds. The following compounds illustrate those which are included in the definition aliphatic group such as lauryl, tridecyl, myristyl, cetyl, stearyl, arachidyl, etc. Quaternary salts of organic nitrogen bases are especially suitable, such as e.g., quaternary ammonium of long chain cationic compounds which can be used, for example:

triphenylmethyl phosphonium iodide triphenylbcnzyl phosphonium iodide N-methylbenzothiazolium iodide trimethylbenzylammonium iodide diethylmethyl-p-acetamidophenyl-ammonium iodide N-ethyl-6-methyl-quinolinium iodide N-methyl-Z-iodoquinolinium iodide 2-methyl-3-ethyl-4,5-diphenylthiazolium iodide benzyltrimethyl-ammonium hydroxide diisobutylphenoxy-ethoxy-ethy1-dimethyl-benzyl ammonium chloride benzylalkonium chloride,

lauryl aceto piperidinium sulfate cetyl pyridinium bromide, etc.

Iodide Ions The iodide ions are preferably supplied from alkali metal salts; such as, for example, potassium, sodium, and the like, preferably potassium iodide; however, other iodide salts can be used as well as any compounds which provide iodide ions including organic materials which disassociate in aqueous solution.

Heterocyclic Organic Compound The heterocyclic organic compounds which are useful in this invention include those having one or two rings. The heterocyclic rings may contain 5-12 atoms in the rings and preferably contain at least one nitrogen atom, such as, for example, pyridine, quinoline, quinoxaline, pyridopyridine, quinazoline, pyridazine, pyrimidine, pyrazine, pyrrole, pyrazole, isoindole, indole, pyrindine, indazole, pyridinium salts, etc.

Preferred heterocyclic organic compounds having a nitro group bonded to an aromatic nucleus may be represented by formulas III, IV, V and VI.

III

wherein each of R R R R R is H, alkyl (1-20 carbon atoms), N0 COOH, COOR (R' is alkyl 1-20 carbon atoms) at least one of R R and R being NO IV R Hal 4 R:

wherein R is CH I, R and R or R and R complete a nitro-substituted aromatic carbocyclic ring fused onto the cyclic ammonium ring and each of R and R is an alkyl group (1-20 carbon atoms) or a halogen-substituted alkyl group (1-20 carbon atoms). V 1'1 wherein R or R is N0 the remaining group is H or CH or a halogen substituted methyl group. Compounds of this formula V may have additional substituents.

where R is alkyl having 1 to 20 carbon atoms or aralkyl having 1 to 20 carbon atoms and X is an anion.

A preferred heterocyclic organic compound is 1-(2',4'- dinitrophenyl)pyridinium chloride but other organic compounds 'which can be used, for example, include:

CATIONIC COMPOUNDS Cationic heterocyclic compounds without the nitro group include all of the cationic heterocyclic rings mentioned above in connection with the nitro-substituted compounds but are not nitro substituted. Preferred compounds contain at least 10 carbon atoms. They are typically substituted with a group selected from the class consisting of alkyl, cyano, phenyl, halide, etc. Preferred organic cationic compounds having an aromatic group but no nitro group may be represented by formulas VI and VII.

Halide wherein R is alkyl, e.g., methyl, ethyl or cetyl (l-20 carbon atoms); R is H or a lower alkyl group, e.g. methyl, etc., having 1-5 carbon atoms; R is H or substituent such as cyano, alkoxycarbonyl (e.g., ethoxy carbonyl) or R and R have the values given above for formula IV and either R and R or R and R complete a benzene ring fused onto the cyclic ammonium ring.

VII

R VIII H/ wherein R is a long chain alkyl group containing 12-20 carbon atoms and R is a substituent such as acyl, e.g., aceto.

The cationic heterocyclic compounds which can be used include, for example:

1-ethyl-4-ethoxycarbonyl quinolinium iodide 2-methyl-isoquinolinium iodide 1-ethyl-2-methyl-quinolinium iodide 4-cyano-l-ethyl quinolinium iodide 1-ethyl-4-ethylcarboxylatequinolinium iodide Z-methyl isoquinolinium iodide l-cetyl pyridinium bromide l-ethyl quinolinium iodide l-methyl quinolinium iodide 2 3 5 -triphenyl-tetrazolinium chloride 5-chloro-l-ethyl-Z-methyl benzothiazolinium iodide 1-ethyl-2-[3- (2-pyridylaminovinyl) pyridinium iodide Solvents An aqueous medium is employed but the medium can contain a water-miscible alcohol with one or more hydroxy groups, for example, methanol and/or isopropanol and/ or isobutanol so as to increase the solubility of any of the solutes to the desired level. However, it is preferred to keep the concentration of the solvents to a minimum, in order to keep the flash point of the medium as high as possible.

The long chain organic cationic compound can be used in a concentration of about 0.01 to about 10 grams per liter, preferably about 0.05 to about 7 grams per liter.

The iodide can be used in an amount within the range of about 4 to about 50 grams per liter, preferably about 6 to about 16 grams per liter.

The organic heterocyclic compound which has a nitro group bonded to an aromatic nucleus or the aromatic cationic compound can be used in an amount within the range of about 0.5 to about 20, preferably about 4 to about 10 grams per liter.

The pH of the aqueous solution should be such that strongly colored dyes are not formed, i.e., the solution should be acid but the pH is between about 1.5 to about 7, preferably between about 1.7 to about 6. The solution can be buffered at the desired pH and an organic acid; such as, for example, citric acid, lactic acid, acetic acid, etc., can be used for this purpose. Amounts of organic acid between 5 and grams per liter are useful. In a preferred embodiment, about 5 to about 40 grams per liter of an organic acid are used. A buffering capacity is desired on account of the residual alkali that is usually present on the water-accepting surface when the silver image has been formed thereon by the photographic silver salt diffusion transfer process. The pH of the acid aqueous solution should not be raised by such residual alkali which could have the result that strongly colored dyes are formed by the nitro compounds, if present. In addition, an advantage of the present invention in neutralizing any such residual alkali is that formation of soaps by reaction of such alkali with the free fatty acids present in printing inks is thus avoided. Such soaps can cause emulsification of the ink and water used in printing.

Various other components may be added to the fix solution include thickness such as 2-methyl-2,4-pentanediol, hydroxyethylcellulose, carboxymethylcellulose, etc. The keeping or storage stability of the solution is good, but with some fix solutions after 2 to 4 weeks at room temperature, dark crystals begin to form on the bottom of the walls of the container holding the fix solution. These reddish-brown crystals do not dissolve on heating, nor do they interfere with the efficiency of performance of the solution. Crystal formation can be inhibited by raising the pH of the solution to a pH of 4.5 or higher or by adding an antioxidant to the solution or by adding extra solvent. Particularly good antioxidants which may be used in an amount of about 0.1 gram per liter at a pH level below 4.5 include hydroquinone, ascorbic acid, n-propyl gallate, butylated hydroxytoluene, etc., preferably hydroquinone or ascorbic acid.

As indicated above, the water-accepting surface may be the surface of a hydrophilic colloid layer or the surface of a layer of binder containing a hydrophilic pigment. Examples of such hydrophilic colloids are gelatin, polyvinyl alcohol, alginates, carboxymethyl cellulose, etc. Examples of binder layers containing hydrophilic pigments are synthetic hydrophobic polymer layers containing hydrophilic silica particles. Such layers are described, for example in Ormsbee, U.S. Pat. 3,344,741, issued Oct. 3, 1967.

The degree of hydrophilicity is conveniently determined with respect to a drop of a liquid placed on the surface of the material. This can be measured by the contact angle obtained when a drop of distilled Water is placed on a level sample of the coating. By projecting an image of the drop on a suitable screen, and measuring the angle of a line tangent to the dropped image at the point where the drop touches the surface, a contact angle is obtained which can be measured and utilized to determine the de gree of hydrophilicity. For instance, generally a hydrophobic surface has a contact angle of 90 or greater. The contact angle of preferably from about 40 to about 75 indicates the hydrophilicity suitable for adhesion of a hydrophilic coating and is highly desirable for coatings such as gelatin coatings or the like. In connection with silver images on a hydrophilic support, it is generally desirable to have a hydrophilic support which exhibits a contact angle of less than 75 measured with distilled water.

Metal surfaces may also be used for the preparation of lithographic printing plates, including aluminum, zinc, etc .Particularly useful aluminum printing plates are those in which the aluminum surface has been treated to provide an inert hydrophilic surface. For example, the surface can be anodized by employing acids; such as, sulfnric, oxalic, phosphoric, and the like. In a particularly useful embodiment, the surface is anodized as described in Rauner et al., U.S. Pat. 3,511,661, issued May 12, 1970. However, when hydrophilic metal surfaces are employed to receive the silver image, it is preferable to use an aromatic heterocyclic compound without a nitro group instead of the nitro-substituted compound since the nitrosubstituted compound tends to oxidize too strongly for silver images on metal plates.

Any suitable support may be used for the hydrophilic surface including polymeric materials; such as, cellulose esters, poleysters; such as, polyethylene terephthalate, polyamides, etc.

Precipitating agents which are particularly useful for use in the hydrophilic layer for formation of the silver image by a black and white diffusion transfer process include nuclei which are useful as precipitating agents with a silver halide complex, including all of those which are commonly useful in the diffusion transfer process. Nuclei which can be employed include silver precipitating agents known in the art such as sulfides, selenides, polysulfides, polyselenides, heavy metals, thiourea, stannous halides, heavy metal salts, fogged silver halide, Carey Lea silver, and complex salts of heavy metals with a compound such as thioacetamide, dithiooxamide and dithiobiuret. As examples of suitable silver precipitating agents, reference may be made to U.S. Pats. 2,698,237, 2,698,238, and 2,698,245 issued to Edwin H. Land on Dec. 28, 1954, U.S. Pat. 2,774,667 issued to Edwin H. Land and Meroe M. Morse on Dec. 18, 1956, U.S. Pat. 2,823,122 issued to Edwin H. Land on Feb. 11, 1958, U.S. Pat. 3,396,018 issued to Beavers et al. Aug. 6, 1968 also U.S. Pat. 3,369,- 901 issued to Fogg et al. Feb. 20, 1968 and U.S. Pat. 3,532,497 issued to Goffe Oct. 6, 1970. The noble metals, silver, gold, platinum, palladium, etc., in the colloidal form are particularly useful.

Noble metal nuclei are particularly active and useful when formed by reducing a noble metal salt using a borohydride or hypophosphite in the presence of a colloid. The metal nuclei can be prepared in the presence of a proteinaceous colloid such as gelatin and coated on the receiving sheet. The same or a different colloid may be added if desired. It will be appreciated that the coating composition generally contains not only nuclei, but also reaction products which are obtained from reducing the metal salt.

It will also be appreciated that the nuclei or silver precipitating agent may be incorporated in the lithographic layer itself by adding a suitable silver precipitant to the coating composition including the silica, titanium dioxide, polymeric material, etc. By incorporating the silver precpitating agent n the coating composition itself, a lithographic layer and silver precipitating material can be coated in one operation.

Inasmuch as the preferred image obtained by the diffusion transfer process is a silver image at the surface of the receiving sheet, a minimum of hinder or dispersing agent is employed to contain the nuclei or silver precipitating agent. However, various colloids can be used as dispersing agents or as binders for the precipitating agents in the receiving layer. Any suitable colloids can be used. Particularly useful colloids are hydrophilic colloids which are used for binders in silver halide emulsions. Advantageously, they are coated in a range of about 5-5000 mg./ft. Included among suitable colloids are gelatin, preferably coated at a level in the range of about 7-100 mg./ft. polymeric latices such as copoly(2-chloroethylmethacrylate-acrylic acid) preferably coated in the range of 15-350 mg./ft. in a polymeric vehicle containing two components (1) polyvinyl alcohol, and (2) inter-polymer of n-butylacrylate, 3-acryloyloxypropane-1-sulfonic acid, sodium salt and Z-acetoacetoxyethyl methacrylate, in a preferred range of about 10-300 mg./ft.

It will also be appreciated that the precipitating agents can be formed in situ or can be applied by precipitating or evaporating a suitable precipitating agent on the surface.

The hydrophilic layers in the lithographic plate blanks of our invention may also have therein particles, such as silica, bentonite, diatomaceous earth such as kieselguhr, powdered glass, micro crystalline asbestos and fullers earth. In addition, colloidal particles of metal oxides such as titanium dioxide, colloidal alumina, coarse aluminium oxide, zirconium oxide and the like may be used with the nuclei in the receiving layers.

In carrying out the diffusion transfer process, conventionally a silver halide emulsion is exposed to a light image after which it is contacted with a silver halide developing agent containing a silver halide complexing agent. The exposed emulsion is developed in the light struck areas and the unexposed silver halide is complexed with the silver halide complexing agent after which the emulsion is contacted against a receiving sheet and the silver halide complex diffuses imagewise to the receiving sheet containing a silver precipitant.

It will be appreciated that in one embodiment of the diffusion transfer process, an integral element is employed in which an unhardened silver halide emulsion is located over the nucleated layer. After the element has been exposed, the silver halide emulsion is developed employing a silver halide solvent to form a silver image in the nucleated layer. The unhardened silver halide emulsion is then removed, typically by using hot Water. The silver image is then treated according to my invention to improve the oleophilic nature of the silver image.

The following examples are included for a further understanding of the invention.

Example 1 A sheet of negative material is prepared as follows:

Paper base weighing grams per square meter is first made developer resistant by applying to one side a coating of pigmented polyethylene at the rate of 15 grams per square meter and on the other side a coating of unpigmented polyethylene at the rate of 10 grams per square meter. This coated base is given a hydrophilic surface by subjecting the pigmented coating to a high voltage discharge. The hydrophilic surface is then coated with an orthosensitized high contrast silver chloride emulsion at a rate equivalent to 1.5 grams per square meter of silver nitrate, the gelatin content of the emulsion being 0.5 gram per square meter. The emulsion contains formaldehyde as a hardening agent. This sensitive element is exposed to a light image and passed in contact with a polyethylene coated paper receiver having thereon a hydrophilic lithographic coating over which has been coated a layer of silver precipitating nuclei through a solution composed of:

Hydroquinone 15.00 1-phenyl-3-pyrazolidone 1.00 Sodium Hydroxide 13.00 Sodium Sulfite (anhyd.) 75.00 Sodium T hiosulphate pentahydrate 8.00 Potassium Bromide 0.35 Carboxymethyl hydroxyethyl cellulose 5.00

The sheets are squeegeed together and separated after about 20 seconds. The imaged receiver is then treated with the following fix solution of the invention, which is applied evenly with a cotton wool pad. I

The treated polyethylene based receiver is then placed on a lithographic printing press, and wet with water. The forme rollers are dropped and after allowing 10 revolutions of the press on inking, 5 on imaging) clean sharp copies are immediately obtained.

The phrase 5 on inking, 5 on imaging means that the roller bearing the plate is rotated 5 times in contact with the wetting and inking rollers only and then is rotated a further 5 times in contact with the offset roller and the wetting and inking rollers and only after these rotations is the paper brought into contact with the printing roller.

Examples 27 As Example 1 except l-(2',4 dinitrophenyl)pyridinium chloride is replaced by one of the following:

G. 1(2',4,6'trinitrophenyl) picolinium chloride 2 (3) 1(2',4',6'trinitrophenyl) pyridinium chloride 2 (4) 1(2nitro-4-carboxy phenyl) pyridinium chloride 2 (5) 8-nitroquinolinium methiodide 2 (6) S-nitroquinoline 2 (7) p-nitrobenzyl trimethyl ammonium chloride 2 Examples 8-13 As Example 1 except that 1-(2',4'dinitrophenyl) pyridinium chloride is replaced by one of the following:

Examples 14-18 As Example 1 except cetyl pyridinium bromide is replaced by one of the following: (14) Cetyl dimethyl benzyl ammonium chloride (15 Benzyl trimethyl ammonium chloride (16) Lauryl aceto piperdinium sulfate (17) Triphenylmethyl phosphonium iodide (18) N-ethyl-6-methyl quinolinium iodide Example 19 As Example 1 except the negative after exposure is passed through the developer in contact with a paperbased receiver having an image-receiving layer composed of propylene gylcol alginate and gelatin and having the silver precipitating agent distributed on the surface of the layer. Also the imaged receiver is left exposed to the air for half an hour before fixing.

In the above Examples 2-6, clean, sharp copies are obtained using each of compounds (2), (3), (4), (5) and (6) in turn as component (a). Using compound (7) the copy obtained is not as clean and sharp. Clean, sharp copies are also obtained using each of compounds 8 to 13 in turn as component (a). Very good, clean and sharp copies are obtained using each of compounds 1418 in turn in place of component (b). With compound (11) a two-component system is used.

A good clean, sharp copy is obtained also in Example 19.

Photographic silver halide emulsions, preparations, addenda, processing and systems which may be used in connection with preparing the image treated according to this invention are disclosed in Product Licensing Index, Volume 92, December 1971, Publication 9232, pages 107-110, paragraphs I-XII, XV-XVIII, and XXIII.

The invention has been described with particular reference to preferred embodiments thereof but it will be understood that variations and modifications can be eflFected within the spirit and scope of the invention.

I claim:

1. A composition for improving the oleophilic character of a silver image, comprising an acidic aqueous solution containing:

(A) a long chain aromatic cationic compound havin wherein R is alkyl or aralkyl having 12 to 20 carbon atoms, each of R and R is alkyl having 1 to 20 carbon atoms or aryl having 6 to 20 carbon atoms, R" is aryl having 6 to 20 carbon atoms, Y is ZCH COC or ZCH CH OS6 in which Z is a halide ion, and X is an anion, or said long chain aromatic compound is a ternary sulfonium compound containing a long alkyl chain of from 12 to 20 carbon atoms,

(B) iodide ions, and

(C) a compound containing a heterocyclic nucleus having 5 to 12 atoms composed of carbon atoms and one or two nitrogen atoms, either 1) one of said nitrogen atoms being a quaternary atom of an ammonium group, or (2) said compound comprising a nitro group substituted aromatic ring or the combination of (1) and (2) above.

2. A composition of Claim 1 wherein said long chain aromatic cationic compound is a quaternary ammonium compound having the formula n l lrirvn 9 1 1 wherein R is alkyl or aralkyl having 12 to 20 carbon atoms, each of R and R' is alkyl having 1 to 20 carbon atoms or aryl having 6 to 20 carbon atoms, R" is aryl having 6 to 12 carbon atoms and X is an anion.

3. A composition of Claim 1 wherein said long chain aromatic cationic compound is a ternary sulfonium compound containing an alkyl chain of from 12 to 20 carbon atoms.

4. A composition of Claim 1 wherein said compound comprising a heterocyclic nucleus has the formula wherein R R R R and R are each H, alkyl having 1 to 20 carbon atoms, N COOH, COOR' (R' is alkyl having 1 to 20 carbon atoms), and at least one of R R and R is N0 X is a halogen ion.

5. A composition of Claim 1 wherein said compound comprising a heterocyclic nucleus has the formula wherein R is alkyl (1-20 carbon atoms), R and R or R and R complete a nitro-substituted aromatic carboxylic ring fused on to the cyclic ammonium ring and each of R and R is an alkyl group (1-20 carbon atoms) or a halogen-substituted alkyl group (1-2-0 carbon atoms); X is a halogen ion.

6. A composition of Claim 1 wherein said compound comprising a heterocyclic nucleus has the formula wherein R or R is N0 the remaining is H or CH or a halogen-substituted methyl group.

7. A composition of Claim 1 wherein said compound comprising a heterocyclic nucleus has the formula wherein R is alkyl having 1-2O carbon atoms, X is a halo gen ion or sulphate ion.

8. A composition of Claim 1 wherein said compound comprising a heterocyclic nucleus is l-cetyl pyridinium bromide.

12 9. A composition of Claim 1 wherein said compound comprising a heterocyclic nucleus has the formula wherein R is alkyl (120 carbon atoms), R is H or an alkyl group (l-5 carbon atoms), R is H or cyano or alkoxy carbonyl, or R and R have the values given above and R and R or R and R complete a benzene ring fused on to a cyclic ammonium ring; X is a halogen ion. 10. A composition of Claim 1 wherein said compound comprising a heterocyclic nucleus has the formula wherein R is a long chain alkyl group containing 12-20 carbon atoms and R is acyl.

11. A composition of Claim 1 wherein said compound comprising a heterocyclic nucleus is 1-(2',4'-dinitrophenyl) pyridinium chloride.

12. A lithographic element comprising a support having thereon a hydrophilic surface and having thereon a silver image having been treated with the acidic aqueous solution of Claim 1.

13. An element of Claim 12 in which said long chain aromatic cationic compound is diethylmethyl-p-acetamidophenyl-ammonium iodide.

14. An element of Claim 12 in which said compound comprising a heterocyclic nucleus is 1-(2,4-dinitrophenyl) pyridinium chloride.

15. An element of Claim 12 in which said silver image is formed by a photographic silver diffusion process.

16. A process of improving the oleophilic character of a silver image comprising contacting said image with the acidic aqueous solution of Claim 1.

17. A process of improving the oleophilic character of a silver image comprising contacting said image with the acidic aqueous solution of Claim 2.

18. A process of Claim 16 in which said long chain aromatic cationic compound is a ternary sulfonium compound containing an alkyl chain having 12 to 20 carbon atoms.

19. A process of Claim 16 in which said long chain alkyl cationic compound is diethylamethyl-p-acetamidophenylammonium iodide.

20. A process of Claim 19 in which'said compound comprising a heterocyclic nucleus is 1-(2',4-dinitrophenyl) pyridinium chloride.

21.. A process of Claim 16 in which said silver image is formed by a photographic silver diffusion process.

References Cited UNITED STATES PATENTS 3,676,125 7/1972 De Haas 96-29 L 3,063,837 11/1962 Lassig et a1. 96-33 3,161,528 12/1964 Hepher et a1 9633 J. TRAVIS BROWN, Primary Examiner R. L. SCHILLING, Assistant Examiner US. Cl. X.R. 96-33; l0l466 PAGE 1 f 2 UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,832,175 DATED I Au ust 27, 197A lNVENTOR(S) I Rodney J Kemp It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 60, strong should read ---strong1y---.

Column 3, line 69, "bromine" should read --bromide--.

Column 7, lines 35-36, "sulfnric" should read ---su1furie---. Line 46, "poleysters" should read ---po1yesters--.

Column 8, lines 11-12, "precpitating" should read ---precipitat;ing--.

Column 11, line t-O, delete alkyl (1-20 carbon atoms)" and insert; C11 1 Column 11, line 58, after "remaining" insert ---group--.

Lines 62-68, the formula should read as follows:.

PAGE 2 f 2 UNITED STATES PATENT AND TRADEMARK OFFICE EERTIFICATE OF CORRECTION Q PATENT NO. 1 3,832,175

DATED August 7, 197

INVENTORtS) I d y J Kemp It is certrfred that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column l2, lines t-lO, the formula should read as follows:

l 1 X R 7 Column l2, lines 20-25, the formula should read as follows:

H reg N Column 12, line 56, "dietlhylamethyl should read a ---diet:hylmethyl,

Signed and Scaled this eleventh Day of May 1976 [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN Aucsrmg Officer ('ummr'ssimur uj'larenrs anu' Trarlcmurkx 

